Yellow-white bicolor. Adopted 22 October 1892. In use for local and regional authorities since 1952.
Norman Martin, 9 Sep 1996

The colours of the [Prussian] province adopted in 1887 were the same as the ones of the former kingdom: yellow over white. This flag can still be seen today, but is rarely used. The coat-of-arms of the Prussian province and later Land of Hanover was Gules a horse Argent. It can still be used.
Pascal Vagnat, 9 Sep 1996

[According to the website of the Hanoverian monarchists] after the Prussian annexation, in 1873, a provincial flag was designed with the lion of Lüneburg instead of the horse, but this was so unpopular, that finally in 1881 the horse was readopted (without the green field).
Norman Martin, 26 June 2000